Baltimore City features 130 miles of Prestressed Concrete Cylinder Pipe (PCCP), 15 percent of which is Class IV PCCP installed in the 1970s. This particular class of pipe has been prone to early failures across the United States, making it a major priority for BPW as it renews its water and wastewater infrastructure.

The Gwynns Falls/Southwestern Transmission Main, made of 54-inch PCCP, is a critical supply of water to some of BPW’s 1.8 million customers.

In March 2012, BPW contracted Pure Technologies to complete an electromagnetic (EM) inspection using PipeDiver to determine the baseline condition of the pipeline. The tool is free-swimming and able to quantify the amount of wire breaks in PCCP.

The same pipeline was already equipped with an Acoustic Fiber Optic Monitoring System installed during a 2007 project with Howard County. The system gives The City an early warning when prestressed wires break in their PCCP, ultimately allowing intervention on rapidly deteriorating pipes to prevent failures.

The results from the baseline EM inspection showed that the pipeline has broken wires in several sections. In the months following the inspection, the situation became critical when the AFO system detected a string of wire breaks in the same area, which led to the recommendation to remove a badly distressed pipe section.

A feature story on WBAL-TV 11 from July 17, 2012 shows BPW and Pure verifying the condition of the Gwynns Falls/Southwestern Transmission Main after the city shut down the pipeline.

BPW's decision to shut down the transmission main and replace a distressed section prevented a major pipe failure. Upon verification, BPW and Pure determined that the pipe section was in a state of near failure and that the monitoring system had correctly identified the distressed pipe.

The verification confirmed the location of the wire breaks through impact testing

A visual inspection identified two large cracks in the pipe creating a hollow section; this confirmed that a failure could have occurred at any time

The damaged pipe was removed from the ground and the pipe was returned to operation on Saturday, July 21, 2012

Preventing the failure allowed The City to avoid significant environmental damage, service disruption and financial cost. The average large-diameter pipe failure costs US$ 1.8 million to remediate

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